1. Field of the Invention
The present invention relates to a stereoscopic image display method that permits an observer to observe a stereoscopic image without special glasses and a stereoscopic image display apparatus using the method and, more particularly, to a stereoscopic image display method and a stereoscopic image display apparatus that are adapted to display a stereoscopic image in such a manner that a synthetic parallax image obtained by alternately arranging stripes of parallax images from two or more view points in a predetermined order is displayed on an image display element such as a CRT or an LCD, light from the image is condensed onto a mask pattern by an optical system consisting of a lenticular lens or the like placed in front of the image display element to transmit only predetermined parallax image light, and the parallax image light transmitted by the mask pattern is converged at predetermined view point positions on an observation surface by an optical system placed in front of the mask pattern, and that are preferably applicable to stereoscopic display, for example, in television, video, and computer monitors, game machines, and so on.
2. Related Background Art
The parallax barrier and lenticular methods are well-known as conventional methods of stereoscopic image display in which the image display element such as the CRT or the LCD displays the synthetic stripe parallax image obtained by alternately arranging stripes of parallax images from two or more view points in a predetermined order and in which the display light from the parallax image is guided only to the view point positions corresponding to the parallax images by the optical member placed in front of the image display element.
For example, Japanese Patent Application Laid-Open No. 9-311294 proposes the stereoscopic image display method and apparatus wherein light from an illumination light source is guided through a mask pattern having predetermined opening and shield portions so as to pattern beams transmitted thereby, the transmitted beams are provided with directivity by an optical system patterned so as to guide the patterned beams separately to the right eye and to the left eye of the observer, a transmissive image display element is interposed between the patterned optical system and the observer, and the parallax images corresponding to the right eye and to the left eye are displayed in a synthetic pattern of alternate stripes on the image display element.
In the parallax barrier and lenticular methods, the synthetic stripe parallax image is a vertical stripe synthetic parallax image in which vertically long stripes of parallax images are alternately displayed, and the directing of the parallax images toward the view points is effected by parallax barriers or lenticular lenses placed in front of pixel positions of the vertical stripe images and in front of the image display element. When an image display element having discrete pixels such as a CRT or an LCD is used as an image display element in these methods, dark portions without display light appear on the observation surface in correspondence to the so-called black matrix part between pixel and pixel, so as to narrow down the horizontal width of the effective observation area.
In the method proposed in Japanese Patent Application Laid-Open No. 9-311294, a transmissive image display element such as an LCD is used as an image display element and the directing of the display light toward the positions of the left and right eyes is effected by directing the illumination light by an optical system placed behind the image display element. In this method, crosstalk occurred in certain cases if the direction of the display light was disturbed, for example, by diffusion in the transmissive image display element such as the LCD or by diffraction in the pixel structure.